The present invention is directed generally to molds for use in injection molding machines and to guide elements for guiding relative movement of some portions of the molds with respect to other portions. The present invention is more particularly related to guides for use in three portion molds consisting essentially of a mold cavity assembly, a mold core assembly and an intermediate assembly including space surface defining elements that cooperate with the mold core and cavity assemblies to define the space in which articles are molded of plastic, the guides regulating the movement of the space surface defining elements during movement of the intermediate assembly relative to the other portions of the mold. The invention has particular utility in a molding machine used in conjunction with a molded article receiver unit designed to enter into an interval or opening between the mold cavity assembly and the other mold assemblies subsequent to formation of the molded article wherein the invention permits adjustment of the position and/or timing of release of the molded article from the intermediate assembly into the molded article receiver unit.
Brun, Jr. , et al., U.S. Pat. No. 5,531,588 discloses an adjustable cam track for an injection molding machine having a base, the machine including a mold having a mold cavity assembly, a mold core assembly that is movable relative to the mold cavity assembly, and a stripper assembly movably interposed between the mold core and cavity assemblies. The stripper assembly has at least one pair of space defining surfaces which together with the mold cavity and core assemblies defines at least one space for receiving plastic material injected therein to form at least one molded article. A first motive means moves the mold core assembly and the stripper assembly away from the mold cavity assembly to remove the at least one molded article from the mold cavity assembly. A second motive means separates the mold core assembly and the stripper assembly to remove the at least one molded article from the mold core assembly. The adjustable cam track of Brun, Jr. , et al., comprises generally a guide fixed to the stripper assembly. A cam follower is coupled to the space defining surfaces of the stripper assembly platen and engaged in the adjustable cam track for causing relative movement of each pair of space defining surfaces to release the molded article from the molding machine. The adjustable a cam track also includes a cam insert that is adjustably positionable with respect to the guide to adjust the point of release of the molded article. The cam insert includes a first toothed rack, and a second toothed rack removably fixed to the guide and engaging the first toothed rack to fix the position of the cam insert relative to the guide only at certain preselected locations.
The adjustable cam track of Brun, Jr., et al., has been used in the manufacture of parisons for containers at rates that required special handling of the parisons upon their removal from the mold core assembly. This special handling was accomplished with a molded article receiver assembly that was movable into the interval between the mold cavity assembly and the mold core assembly when the mold was in an open position such as that disclosed in Delfer III, U.S. Pat. No. 4,721,452. Ideally, the movement of the stripper assembly relative to the mold core assembly inserted the parisons into the molded article receiver assembly and the release of the parisons by the pair of space defining surfaces occurred only when the parisons were properly located in the molded article receiver assembly. However, as a practical matter, even slight misalignment between the mold core assembly and the molded article receiver assembly caused one or more of the parisons to be significantly damaged as they were inserted into the molded article receiver assembly. While substantial efforts were focused on insuring the proper alignment between the mold core assembly and the molded article receiver assembly during the movement of the stripper assembly, this did not always accomplish the desired end.
It is therefore desirable that each pair of space defining surfaces of the stripper assembly be allowed to separate slightly, but not entirely, from the molded articles so that the molded articles are only loosely retained in a prerelease position. This prerelease position allows some play in the position of the molded articles relative to the stripper assembly thus permitting some variation in position of the molded article receiver assembly at the time of introduction of the molded articles. Due to the variation in length of the molded articles, it is also desirable to modify or adjust the position of product release from the stripper assembly in relation to the position of onset of the prerelease position.
In accordance with the present invention, an adjustable cam track is provided that includes a prerelease position and includes provision for modifying or adjusting the position of product release from the stripper assembly in relation to the position of onset of the prerelease position. The adjustable cam track of the present invention can be used in conjunction with any mold assembly that includes a first mold portion, a second mold portion movable with respect to the first mold portion, a third mold portion movably interposed between the first and second portions, the third mold portion having at least one pair of space defining surfaces which together with the first and second mold portions defines, in a closed position, at least one space for receiving plastic material injected therein to form at least one molded article. The second and the third mold portions are movable away from the first mold portion to permit removal of the at least one molded article from the first mold portion, and the second mold and third mold portions are movable away from each other to remove the at least one molded article from the second mold portion.
The adjustable cam track of the present invention includes a guide coupled to the second mold portion, the guide defining a first portion of the adjustable cam track. A cam follower is engaged in the cam track and is coupled to the at least one pair of space defining surfaces of the third mold portion for causing relative movement of each pair of space defining surfaces as the third mold portion moves relative to the second mold portion. The cam follower is engaged in the first portion of the cam track when the mold portions are in the closed position. The first portion of the cam track also includes a ramp to an intermediate portion defining the prerelease position of each pair of space defining surfaces so that the at least one molded article is loosely retained by the space defining surfaces. The adjustable cam track of the present invention also includes a cam insert defining a second portion of the adjustable cam track. The path defined by the cam insert is generally a matter of choice of design except that it includes the point of release of the at least one molded article from the space defining surfaces. The cam insert is adjustably positionable with respect to the guide to adjust the point of release with respect to the ramp defining the onset of prerelease, thereby permitting the adaptation of the cam track to molded articles of a variety of sizes.
In a preferred embodiment, the guide and the cam insert of the adjustable cam track of the present invention include a set of interlocking lands and grooves providing continuous engagement during adjustment of the position of the cam insert relative to the guide. Preferably, the set of interlocking lands and grooves are provided on a first pair of confronting walls, and the guide includes an undercut at the base of another wall, and the cam insert includes an outwardly extending flange engaging the undercut to facilitate slidable adjustment of relative position between the guide and the cam insert.
Also, in a preferred embodiment, the adjustable cam track of the present invention includes a first toothed rack fixed to the cam insert. A second toothed rack is coupled to the guide and engages the first toothed rack to fix the position of the cam insert relative to the guide only at certain preselected locations.
Additionally, in a preferred embodiment, the adjustable cam track of the present invention is constructed so that one of the guide and cam insert includes at least one index mark, and the other of the guide and cam insert includes a plurality of graduation marks alignable with the at least one index mark to indicate a selected position of said point of release.
Other features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the illustrated preferred embodiment shown in the accompanying figures showing the best mode of the present invention as understood by the inventors.